ESA and ANU make space propulsion breakthrough[i]The European Space Agency and the Australian National University have successfully tested a new design of spacecraft ion engine that dramatically improves performance over present thrusters and marks a major step forward in space propulsion capability.
...
The new engine is over ten times more fuel efficient than the one used on SMART-1. â€œUsing a similar amount of propellant as SMART-1, with the right power supply, a future spacecraft using our new engine design wouldnâ€™t just reach the Moon, it would be able to leave the Solar System entirely,â€

All things considered I'd be more happy just to have that power supply!
Other things aside, without that power supply it is hard to think of missions for which this level of ISP is valuable. Smart 1 used an ISP which was at least somewhat appropriate for its mission. Maybe I'm overstating things, but I think compared to reducing the cost of reaching orbit to something reasonable all these things to do with optimizing the mass of things in space are often just distractions. If Elon ever gets Falcon 5 launching I hope the cost of *payloads* in space starts to fall with the cost of launch.

And I'm happy they do research on all fields I think the ION drive will help as a little step to add to the inspace capabilities.. and in the end.. more "space" capabilities may push for more "available" space features, adding more demand for the launch industry...

I'm wondering, what's the "minimum" altitude an ion spacecraf "currently" needs (relative to it's mass) to move away of earth, to counter gravity and become "free", and maybe they can put 2 or more ion drives on the same spacecraft. How "lower" they need to put mass into space.. how lower the costs... and for "payloads" I think time is less important or expensive compared to putting people in space. I only fear for ION drives.. their acceleration is too slow.. to do a lot... but maybe they will be able to achieve a lot more in the future based on this or similar technology.

Do you mean if you just dropped a vehicle at zero speed and at some altitude where there is much reduced gravity?

e.g. Smart 1 manages about 1/50000g so it could only hover at about 220 earth-radii which is much further away than the moon itself. Instead smart 1 slowly increases its orbital radius by directly increasing its angular momentum, so it only needs to start out at something like LEO where drag is managable. Not sure exactly what orbit it was placed into before it started under ION engine thrust, but obviously it is one with less energy than lunar orbit. There really isn't going to be much scope for reducing the Delta-V of a booster by switching to ION thrust early on.

Yes.. that was what I had in mind... drop my thaughts out of the first window you see... didn't knew the thrust was so low...
I think the SpaceElevator is my best hope to achieve cheap access to space...but in the mean time.. I really hope SpaceX will succeed.

Seems like interesting breaktrough. However, to gain full advantage, some efficient power source is required. Since ion engine is most useful in the long range missions (outer planets, kuiper objects), solar panels are almost useless.

There's saying "When you're on the Earth orbit, you're in the half way to anywhere". It's good that they found out how to make half of the journey effective and fuel efficent. But they're focusing on the wrong half of the voyage

The result might make ion engines to evolve to a powerful propulsion for manned interplanetary vehicles.

Not necessarily. Ion engines are extremly weak. First space probe with ion engines was Deep Space I. NASA stated that its ion engine generates thrust more or less equal to the weigth of the sheet of paper. If I remember correctly, Smart-1 has 0.1 newton of thrust. If that 10-fold increase is real, then we have only 1 newton propulsion.

It's still many orders of magnitude too weak for manned missions. It's full potential is best used in long duration, long range missions when you gain most from weak, but steady acceleration.

For example, let's think about Mars manned, ion propelled mission for a second. It would have to accelerate half of the journey and then decelerate second half. (Aerobreaking might help a little, but not much).

Apollo got to the Moon in 3 days, Smart-1 required 1,5 year. Ion engines are, and will in a foreseeable future, only for robotic mission, which don't mind spending additional year or two in space.

It's still many orders of magnitude too weak for manned missions. It's full potential is best used in long duration, long range missions when you gain most from weak, but steady acceleration.

Of course for a maned mission you would have to use cemicial rockets for the initial boost. And then you would use the Ultra-ion engines too gain more speed to shorten the travel time.

An remember it said..:
..a small cluster of larger, high power versions of the new engine design would provide enough thrust..So of course it would be more than 1 newton propulsion... And would be used together with some a more powerfull powersource than the sun.

_________________

Last edited by Voyager4D on Fri Jan 13, 2006 2:30 pm, edited 1 time in total.

Alright - I simply referred to their speaking about "an adequate amount of electrical power" and "a small cluster of larger, high power versions of the new engine design".

These words might mean that the factor-10-increase isn't the limit but the increase achieved in the lab only - as if that lab-version isn't a high power version in their view and not as large as if it were used to do a space mission really in their view. They didn't apply a cluster but a single test-sized engine only and are talking as if they can imagine the use of much more electrical power. Then a real used engine of this new design may increase the thrust by much more than a factor of ten.

From my point of view larger versions of the lab-versions, high power versions of the not-that-high power lab version, cluster of such engines instead of a single engine and a higher amount of electrical power already is an evolution of the engine. I suppose that this is not a view of engineering - according to what I said in the Synopsis Technology-thread it is an evolution under the aspect of allocation.

Ion engines are extremly weak. First space probe with ion engines was Deep Space I. NASA stated that its ion engine generates thrust more or less equal to the weigth of the sheet of paper. If I remember correctly, Smart-1 has 0.1 newton of thrust. If that 10-fold increase is real, then we have only 1 newton propulsion. (...)For example, let's think about Mars manned, ion propelled mission for a second. It would have to accelerate half of the journey and then decelerate second half. (Aerobreaking might help a little, but not much).

Apollo got to the Moon in 3 days, Smart-1 required 1,5 year. Ion engines are, and will in a foreseeable future, only for robotic mission, which don't mind spending additional year or two in space.

You need to get your number right, thomson.
The SMART-1 plasma engine produces 68 mN at an ISP of 1640s, using 1190W of power. For SMART-1 with its 367kg mass, that provides around 0,18 mm/s2 of acceleration - enough for SMART-1, but in a Mars mission where you'd want to get there in, say, 3 months, you'd need greater acceleration. Then, what's required is mostly more electrical energy (and a bigger SPT thruster).

The new DS4G thruster, however, has a 21000s specific impulse. That is the (greater than) factor-10 improvement. Its thrust isn't even mentioned in the ESA press release. But this also means that for the same thrust, it needs ten times the electrical power (less if it has better efficiency; the SPT is, I think, only about 45% efficient). It will consume only 10% of the fuel, but this kind of thruster will mostly be interesting in situations where energy is abundandt - like to the inner planets, or using a nuclear power source. However, if you can significantly increase the power-to-mass ratio of a spacecraft, electric propulsion suddenly becomes much more interesting.

Here's a 1991 example study of a manned mars mission with a 400t craft using 10MW of power: http://www.astronautix.com/craft/stcemsep.htm That's about ten times the power-to-mass ratio of SMART-1, and that's where electric propulsion becomes interesting for manned Mars missions. It's just possible with solar power, though at this kind of mass, nuclear power would surely look attractive too. Only mind: This uses 10MW for a 5500s ion thruster. For a 22000s DS4G thruster, you'd use four times the power, and a quarter the propellant.

Regards
Max

_________________There's space for all of us, if each will leave some space for the next one

The ideas expressed above are my own, not necessarily those of my employer.

By 1962 Ernst Stuhlinger's ion-drive Mars expedition had evolved within the Research Projects Division into five 150 m long spacecraft, housing a total crew of 15. A much shorter 475 day mission time was planned.

(emphasis added)

The most recent mission was planned by the Mars Society, and only has room for a crew of 5, who are expected to spend 19 months on the Martian surface. Granted, an extended holiday on Mars would be great, but 19 months is a bit much, don't you think? The sad part is, that's a chemical mission, with a 134-day transport time. Ion missions are planned to take much longer, although the the crew would not be required to stay on the surface as long (since the ion ship is designed to take so long to get back home in the first place, it doesn't much care where it starts from).

Thank You Very Much for that link which I will have to read when I have time to do that.

I am a little bit sorry but I have a systematical problem with your argument this time. You are refrring to something said or written in 1962 while the new engine design has been made public the last few days and so will have been developed very recently - one or two years perhaps.

The study you refer to I suppose to be based not on the new engine design but on another one which is n't as effective as the new one.

Systematically now it has to put in question if the findings of the study will still be valid if it would be based on the new design. To answer the question it is required to redo all the calculations etc. - like I am doing it in the Accumulations-thread in the Financial Barriers section The alternative to doing so is to have one single formular which describes the entire vehicle.

I remember a post where someone argued to me by saying that something special as an important, valid and widely accepted reference point and I suppose that the study you are referring to is such a reference point too. I also remeber that I have read that the development and engineering of rockets started based on experiences which have been put into theories expressing them. So I don't want to argue against that.

But the systematical problem with this is that this way there seems to be no chance to find out the borders of the validity of the reference points, experiences and the like. Thius is one of the reasons why reference points, experiences, empirical data and statistics aren't accepted as arguments in Political Economics as arguments but as a falsification tests of theories only.

Reference points, experiences, empirical data and statistics are accepted in Political Economics as base for decisions etc.

I have no problems with the dimensions etc. of the vehicle studied up to now because I haven't read the study yet and so don't know economical data yet. But even if I would know them already I need economical data got if the study would be based on the new engine design alternatively.

The article about the new design makes me suppose that the economical data based on it would be better than those to be fund in the study. If it would trun out that I am right then this is a progress under the view of economics. The difference in the design of the used engine is a difference in the allocation because a different engine would be allocated to the vehicle. So it is a progress in allocation - and that's an evolution from the view of economics

Very much words but they are meant to explain the systematical problem only which I have. And Iit may be that the lab-version will be developed further, improved and the like - this I always consider too for systematical reasons. I allways tend to do systematical comparisons - it's an instrument like sensors, oscilloscopes and the like.

Does it clarify my systematical problem? I am missing a model or theory which describes a whole space or set of vehicles which the vehicle in the study and a vehicle with the new engine design are special concrete members of - mathematically spoken. ...

If I understand the article correcly then this engine design overcomes the problem of grid voltages which limit how fast ions can be accellerated. The higher the voltage the faster the ions become but because of the proximity of the 2 grids some of the ions cause damage by colliding with the higher voltage grid. By using 2 pairs of grids and moving them further apart stops this happening at higher voltages so ions can go faster.

Since thrust is dependant on exhause velocity, a higher velocity gives more thrust per ion making the engine more efficient. Ignoring the power used for the moment this means that you get more thrust per kg of propellant and an engine having the same throughput of ions as SMART-1 would have a lot more thrust.

Getting back to the power being consumed, it does not necessarily follow that having a much higher voltage requires much more power, that said there is no such thing as a free lunch and there is likely to be an increase in power consumed, a 10 fold increase in voltage might allow a smaller drive current to be used so power need not rise by the same amount. Also some of that power is used to generate the ions in the first place and since we are talking about the same amount of ions being produced this should not alter.

I'm not sure you need to generate Megawatts of power to get enough accelleration from an ion engine to be able to use it on a manned craft. While it is never going to push you back in your chair a few kilograms could work OK.

_________________A journey of a thousand miles begins with a single step.